The Z-25 Šohaj was designed to be a replacement for the pre-war,
German Meise. The latter, designed for the glider competitions of the 1940
Olympics that were abandoned because of hostilities, was widely used in post-war
Czechoslovakia. The two types had similar appearances and much in common but the Šohaj significantly improved on the older aircraft by using 5-digit series
NACA airfoils rather than the old Göttingen 549; the NACA sections provide more lift at low speeds, improving flight in
thermals and lower landing and take-off speeds. They also had a lower
pitching moment and hence lower tail loads, allowing the structure to be lightened. The Šohaj's wings were mounted around
shoulder height on the
ovoid cross section
fuselage, enabling a smoother aerodynamic junction than on the Meise, which had a high wing on an almond shaped fuselage. The Šohaj is an all wood-framed aircraft, covered in a mixture of
plywood and
fabric. It has strongly straight tapered wings (taper ratio 0.28) with elliptical tips, built around a single
spar. From the spar forward around the
leading edge the wing is ply covered, forming a torsion resistant D-box. Behind the spar the wing is fabric covered except near the roots ahead of an internal, diagonal, drag strut. There is no sweep at one quarter
chord and the wings are mounted with 3° of
dihedral. Fabric covered
ailerons fill about half the span, with
airbrakes just inboard of them and immediately aft of the spar. On the early
Šohaj 1, first flown in 1947, these are of the
DFS type like those on the Meise, opening above the wings. These are also fitted to the
LG-125 Šohaj 2 (sometimes written as
Z-125) but the later
VT-425 Šohaj 3 or
Super Šohaj of 1955 has parallelogram action, double blade
Schempp-Hirth type airbrakes. The Šohaj 3 also had its wingspan extended from to and was fitted with inboard flaps of the
Fowler type, alterations which improved the
glide angle, reduced the
stalling speed and, through the increased
wing loading, raised the maximum cross country speed between thermals. The fuselage of the Šohaj is completely ply skinned, tapering to the tail. The single seat
cockpit, placed just ahead of the wing leading has a side opening, single piece, blown
perspex canopy. On the first two variants this was short, with an abrupt forward profile but on the Šohaj 3 it was lengthened to the nose, with a much smoother contour. At the rear these canopies merge into the fuselage forward of and over the wing. The fixed tail surfaces have straight leading edges and are ply covered, with rounded, fabric covered control surfaces. The
tailplane is mounted just above the fuselage, sufficiently far forward for the
elevators to be ahead of the deep
rudder, which is protected by a tail bumper. There is an elevator trim tab to adjust for different pilot weights The Šohaj 1 lands on a simple, rubber sprung skid but the later models have a fixed, semi-recessed
monowheel just behind the skid which now ends under mid-wing. ==Operational history==